Exhaust manifolds experience thermal cycling as they undergo repeated heating and cooling. Exhaust manifolds operate in a high temperature environment (e.g., in an environment with temperatures around or greater than 1000° C.), which may approach the operating limits of the material from which it is constructed. Such materials include austenitic and ferritic cast iron and austenitic and ferritic cast stainless steel. Specifically, exhaust manifolds may be cast out of these materials. Over the life of an engine an exhaust manifold may heat up and cool down many times, which may cause distortion. During a hot phase, an exhaust manifold may expand up to 3 mm in length, for example. When the exhaust manifold cools down, however, the manifold may contract (e.g., permanently contract). This results in the exhaust manifold contracting to a shorter length than initially desired, such that after many thermal cycles the exhaust manifold is 3 mm shorter in length compared to its original length, for example. During the contraction phase, hotter sections of the manifold may have lower strength and consequentially can experience permanent plastic deformation. This distortion may cause excessive internal stress and ultimately breakage of the exhaust manifold resulting in exhaust gas leakage.
The inventors herein recognize the above described problems and to address these problems, at least partially, propose a cylinder head of an engine, including a plurality of exhaust outlets distributed along a longitudinal axis of the cylinder head, each exhaust outlet of the plurality of exhaust outlets configured to align with a corresponding exhaust gas transfer tube of an exhaust manifold, each exhaust outlet of the plurality of exhaust outlets including a mating surface configured to receive flanges on the corresponding exhaust gas transfer tube, and at least two abutment shoulders, each of the at least two abutment shoulders associated with a different exhaust outlet of the plurality of exhaust outlets and extending beyond a respective mating surface, the at least two abutment shoulders integral with a remainder of the cylinder head, each of the at least two abutment shoulders having an abutment surface configured to interface with the corresponding exhaust gas transfer tube to restrict a lengthwise contraction of the exhaust manifold.
In one example, a cylinder head of an engine may include a mating surface for receiving an exhaust manifold, a first abutment shoulder extending beyond the mating surface and including a first abutment surface, and a second abutment shoulder extending beyond the mating surface and including a second abutment surface, the first abutment shoulder and the second abutment shoulder integral with the remainder of the cylinder head, each of the first abutment surface and second abutment surface configured to interface with a respective adjoining wall of the exhaust manifold to restrict contraction of the exhaust manifold.
In summary, excessive contraction of an exhaust manifold that experiences thermal cycling may be restricted by providing one or more abutment shoulders on a cylinder head surface mating with the exhaust manifold. Restricting excessive contraction of the exhaust manifold by one or more abutment shoulders on the cylinder head may reduce development of excessive internal stress in the exhaust manifold, thereby increasing the life of the exhaust manifold by preventing the development of cracks.
To avoid unnecessary duplication of effort and repetition of text in the specification, certain features are described in relation to only one or several aspects or embodiments of the invention. However, it is to be understood that, where it is technically possible, features described in relation to any aspect or embodiment of the invention may also be used with any other aspect or embodiment of the invention.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.